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feat(Documentation): add a section on consistent reads

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We have waited too long to document `consistent=true`. Document it!
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Brandon Philips
2014-02-20 15:32:23 -08:00
parent 46d817f91b
commit 035bbc6913
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Documentation/api.md
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@@ -783,6 +783,17 @@ curl -L http://127.0.0.1:4001/v2/keys/
Here we see the `/message` key but our hidden `/_message` key is not returned.
### Read Consistency
Followers in a cluster can be behind the leader in their copy of the keyspace.
If your application wants or needs the most up-to-date version of a key then it should ensure it reads from the current leader.
By using the `consistent=true` flag in your GET requests, etcd will make sure you are talking to the current master.
As an example of how a machine can be behind the leader let's start with a three machine cluster: L, F1, and F2.
A client makes a write to L and F1 acknowledges the request.
The client is told the write was successful and the keyspace is updated.
Meanwhile F2 has partitioned from the network and will have an out-of-date version of the keyspace until the partition resolves.
Since F2 missed the most recent write, a client reading from F2 will have an out-of-date version of the keyspace.
## Lock Module